WO2014009653A1

WO2014009653A1 - Modular control system of an installation for producing containers

Info

Publication number: WO2014009653A1
Application number: PCT/FR2013/051640
Authority: WO
Inventors: Thierry Deau
Original assignee: Sidel Participations
Priority date: 2012-07-13
Filing date: 2013-07-09
Publication date: 2014-01-16
Also published as: EP2872313B1; FR2993199B1; EP2872313A1; CN104428122B; FR2993199A1; US20150321413A1; CN104428122A

Abstract

A control system (32) of an installation (1) for producing containers (2) from blanks (3) made from a thermoplastic material, said installation (1) comprising at least two units (4, 9) for processing the blanks (3) or the containers (2), each provided with at least one station (5, 10) for processing the blanks (3) or the containers (2), said control system (32) comprising a central control unit (33) of the installation (1), at least two control units (36, 46) slaved to the central control unit (33) and each associated respectively with a processing unit (9, 4), and at least two controllers (37, 47) each slaved to a control unit (36, 46) and each associated with at least one processing station (10, 5).

Description

Modular control system of a container manufacturing facility

The invention relates to the field of the manufacture of containers from thermoplastic blanks such as PET (polyethylene terephthalate), the term "blank" covering as much an injection preform as an intermediate container having undergone or several temporary forming operations.

The manufacture of the containers is generally accomplished within an installation which comprises several units for treating blanks or containers, typically a heating unit blanks at a temperature above the glass transition temperature of the material, or a unit forming containers from hot blanks, by blow molding or blow molding in molds by injection of a fluid (including a gas such as air) under pressure.

The forming of containers on an industrial scale requires extremely short cycle times. For an ordinary rate of modern production, of the order of 50000 containers per hour, the cycle time, measured between the introduction of the blank into the mold and the evacuation of the formed container, is between 1 second and 2 hours. seconds only.

Poor impression taking and poor material distribution (often correlated) are frequent defects in shape. It is known that these defects may be related to various machine parameters, including the heating temperature of the blanks, the pressure and the fluid flow, or the drawing speed. These correlations are studied in particular in the documents WO 2008/081107 and WO 2012/035260 in the name of the applicant.

The adjustment of each treatment unit is conventionally entrusted to a specialized operator responsible for verifying that the treatment is carried out according to a predefined setpoint (this setpoint includes, for example, in the heating unit, the heating temperature, the speed of scrolling blanks or the power of a ventilation ensuring the evacuation of a part of the heat, in the forming unit, the set includes in particular the injection pressure, the drawing speed, the control temperature of the mold). Manual corrections are generally applied to the setpoint (insofar as the parameters are adjustable) as a function of the perceived quality of the containers subjectively appreciated by the operator. The application of these corrections is a delicate problem, particularly in view of the subjective nature of the perceived quality and the limited number of containers checked with respect to production rates (several tens of thousands per hour). In fact, the time elapsed between the observation of a defect on a series of containers and the effective application of a manually modified instruction by the operator can result in the disposal of several hundred containers produced in the meantime. .

Automation of the settings is under study, thanks to a strict and systematic analysis of curves characterizing the evolution of parameters such as the temperature of the blanks at the exit of the heating unit, realized by means of thermal cameras, or the injection pressure, made in the mold by means of pressure sensors, cf. the aforementioned documents.

This automation, however, poses implementation difficulties, especially when a drift observed on a processing unit requires a transverse feedback, that is to say a change in the setpoint applied to another processing unit. In practice, this problem occurs for example when it is desired to readjust a blowing curve (that is to say a curve showing, on a cycle, the evolution of the pressure measured in the mold, parameter related to the unit forming) on a theoretical curve by correcting a parameter related to the heating unit (typically the heating temperature, set by changing the transmission power of sources of electromagnetic radiation before which the blanks pass).

To date, there is no solution for reliably and automatically performing such transverse feedback.

A first object of the invention is to optimize the control of a container manufacturing facility.

A second object of the invention is to optimize the quality of the containers produced. A third object is, more specifically, to allow a transverse feedback of the various processing units of the installation, depending on drifts observed in the production.

For this purpose, it is proposed, in the first place, a control system of a container manufacturing facility from blanks made of thermoplastic material, this installation comprising at least two units for treating the blanks or containers, each equipped with at least one treatment station of the blanks or containers, this control system comprising a central control unit of the installation, at least two control units controlled by the central control unit and each associated respectively with a unit of treatment, and at least two controllers each controlled by a control unit and each associated with at least one treatment station.

This architecture makes it possible in particular to divide the control tasks within a container manufacturing facility, to the benefit of better control of the installation, and the quality of the containers produced.

Various additional features may be provided, alone or in combination:

the central control unit is programmed to:

control each slave control unit according to a processing instruction loaded in the control unit,

take into account at least one characteristic point at the central unit by the control unit,

compare this characteristic point with a theoretical point, if a discrepancy is decreed between the characteristic point and the theoretical point, to issue a corrected treatment instruction to a second control unit,

- load the corrected treatment setpoint into the second control unit;

each control unit is programmed to:

control each slave controller according to the processing instruction loaded by the central unit, take into account at least one singular point resulting from a measurement carried out on at least one custom-made processing station of a controller,

calculate a characteristic point according to the singular point or points,

comparing the characteristic point with a theoretical point, if a discrepancy is decreed between the characteristic point and the theoretical point justifying a modification of the processing instruction of another processing unit, communicating the characteristic point to the central control unit; each controller is programmed to:

pilot at least one treatment station according to the treatment instruction,

order at least one measurement at the treatment station,

from this measurement, establish a curve describing a variation of this measurement,

analyze the curve and extract the coordinates of a singular point,

communicate the singular point to the control unit. It is proposed, secondly, an installation for manufacturing containers from blanks of thermoplastic material, this installation comprising at least two treatment units blanks or containers (for example a blanks heating unit and a unit of forming equipped with at least one station for forming the containers from blanks), each equipped with at least one station for treating the blanks or containers, and a control system according to one of the preceding claims.

Other objects and advantages of the invention will become apparent in the light of the description of a preferred embodiment, given hereinafter with reference to the accompanying drawings in which:

Figure 1 is a schematic view showing a container manufacturing plant, comprising a forming unit and a heating unit;

FIG. 2 is a schematic view illustrating in more detail the architecture of the installation: Figure 3 is a schematic view illustrating the angular positions of a wheel of the forming unit;

FIGS. 1 and 2 show diagrammatically a plant 1 for manufacturing containers 2 from blanks 3 made of thermoplastic material, for example PET (polyethylene terephthalate).

The installation 1 comprises at least two units 4, 9 for treating the containers 2 or blanks 3. For simplicity, it is assumed in the following that the blanks 3 are preforms.

Typically, as in the illustrated example, the installation comprises:

a heating unit 4 or furnace, which comprises a series of heating modules 5 each having a radiating wall 6 provided with superimposed sources 7 of infrared radiation and a reflecting wall 8 placed in front of the radiating wall 6 to reflect the portion of radiation not absorbed by the preforms 3,

a blow-molding or stretch-blow molding unit 9 equipped with at least one station 10 (and in this case a series of stations) for forming, the or each forming station being provided with a mold

11 to the footprint of a container.

Conventionally, the preforms 3 at room temperature are introduced into the furnace 4 through an inlet thereof, for example by means of a wheel or a feed conveyor. The preforms 3 are then heated in the oven 4 at a temperature higher than the glass transition temperature of the material (the final temperature of the blanks is of the order of 120 ° C. for the PET, whose glass transition temperature is about 80 ° C).

In the furnace 4, the preforms 3 are for example mounted on pivotable supports 12 or spinners. Each spinner 12 is mounted on a chain running on a driving wheel 13 driven in rotation by a motor 14. The spinner 12 is provided with a pinion 15 which meshes with a rack 16 to drive the spinner 12 in rotation while it is moving through the furnace 4 and thus expose the surface of each preform 3 to the radiation. To evacuate at least a portion of the excess heat produced by the radiating wall 6, the furnace 4 can be equipped with an extraction system comprising for example a fan 17 driven by a motor 18 and positioned at the necks of the preforms 3 .

In addition, the power of the radiation emitted by the radiating wall 6 can be modulated by means of a power variator 19, as in the embodiment illustrated in FIG. 2.

The thermal profile of the preforms 3 is preferably controlled, either directly in the furnace 4 or at the outlet thereof, by means of a thermal sensor 20. According to an embodiment illustrated in FIG. 2, the thermal sensor 20 is a thermal camera pointing to the preforms 3.

At the outlet of the oven 4, the preforms 3 and heated are transferred to the forming unit 9 via a transfer unit (such as a transfer wheel) to be blown or stretched individually blown into a mold 11. The preforms 3 are introduced into the forming unit 9 at a point 21 of charge.

After the forming, the containers 2 are evacuated from the molds 11 from a point of discharge 22 to be directly filled and labeled, or stored temporarily for filling and later labeled. Once filled and labeled, the containers are grouped and packaged, for example in a wrapping unit that wraps each group of containers with a heat-shrinkable film.

As also seen in FIGS. 1 and 2, the forming unit 9 comprises a pivoting wheel 23 on which the forming stations 10 are mounted, and a sensor 24 of the instantaneous angular position of the wheel 23, in the form of example of an encoder (i.e., in practice, an instrumented bearing).

Each forming station 10 is equipped with a nozzle 25 through which a fluid (in particular a gas such as air) is injected into the mold 11. Each forming station 10 is also equipped with an injection device comprising an actuator block 26 connected to the nozzle 25 for controlling the injection of the fluid. In addition, each forming station 10 is provided with a device 27 for measuring the pressure prevailing in the container being formed. In the example shown, the measuring device 27 comprises a pressure sensor mounted at the nozzle 25, in which the pressure during forming is identical to the pressure in the container 2.

According to an embodiment corresponding to a blow-molding forming process, each forming station 10 further comprises a movable drawing rod 28 integral with a carriage 29 mounted in translation relative to a support 30.

The movement of the rod 28 is electromagnetically controlled. For this purpose, the support 30 comprises an electromagnetic track connected to a motor 31, and the carriage 29 is itself magnetic. The sign and the power of the current flowing through the track enable the rod 28 to be displaced according to a predetermined displacement profile, comprising a direction and a speed of displacement.

As illustrated in FIG. 1, the forming stations 10 describe a path (in this case circular) which includes a forming sector F extending from the loading point 21 of the preforms 3 to the point 22 of discharge of the containers. 2 formed, and a sector T buffer, complementary to the forming sector F and extending from the point of discharge 22 to the point of charge 21.

The installation 1 is equipped with a control system 32 comprising a central control unit 33 of the installation 1 and, for each processing unit 4, 9, a dedicated control system 34, 35 which automatically controls the operation of the respective unit 9, 4.

Thus, the forming unit 9 is equipped with a dedicated control system 34 which comprises a master control unit 36 and a series of slave controllers 37 slaved to the master control unit 36.

The master control unit 36 is computerized and comprises, as illustrated in FIG. 2:

a memory 38 in which pilot programs of the forming unit 9 are written,

a processor 39 connected to the memory 38 for applying the instructions of the programs, and

a communication interface 40 connected to the processor 39 for communication with external communicating entities, as will be explained hereinafter. Each slave controller 37 is a programmable logic controller, of the type described in W. Bolton, Programmable Logic Controllers, Newnes, Fifth Edition, 2009.

More specifically, each controller 37 comprises:

a memory 41 in which programs for driving at least one forming station 10 are written,

a processor 42 connected to the memory 41 to apply the instructions of the program,

a communication interface 43 connected to the processor 42 for communication with the master control unit 36 via the communication interface 40,

an input interface 44 connected on the one hand to the processor 42 and on the other hand to the device 27 for measuring the pressure, noted P, in the mold 11,

an output interface 45 connected on the one hand to the processor 42 and on the other hand to the actuator block 26 and to the motor 31 for controlling the drawing rod 28.

As a variant, the input and output interfaces 44, 45 are brought together within a unitary input / output interface.

The controller 37 is programmed to perform the following operations:

piloting the forming station with which it is associated (or each forming station with which it is associated, the controller 37 may for example be associated with two forming stations) for the completion of a complete forming cycle along forming sector F, from the loading of a preform 3 to the point 21 of loading until the unloading of the container 2 formed at the point of discharge 22, according to a loaded formation instruction CF (that is to say inscribed) in the memory 41;

- Take into account a measurement of the pressure P in the mold 11.

The pressure measurement is performed by the pressure sensor 27 continuously or sequentially and regularly, at predetermined intervals (for example 5 ms) and communicated to the processor 42 via the input interface 44;

from the pressure measurement, establish during the forming cycle a blowing curve describing the evolution of the pressure P of fluid in the mold 11 at each instant, denoted by t (in practical at times, measured by the internal clock processor 42, corresponding to the angular positions provided by the sensor 27), this curve (visible schematically in Figure 2) being established by the processor 42 and stored during the cycle;

analyzing at the end of the cycle the blowing curve and extracting the coordinates of at least one singular point S (in particular a local pressure peak, typically a point B as defined in international application WO 2008/081107);

communicate at the end of the cycle the coordinates of the singular point to the master control unit 36.

The forming instruction may comprise pressure and / or flow rate values of the fluid delivered by the actuator block 26, or a profile of displacement of the rod 28 or of any other moving part (for example a coupled mold bottom to the rod 28), in the form of, for example, a curve of the speed of displacement of the rod 28 (or of any other moving part) as a function of its position. The speed of displacement of the rod 28 (or of any other moving part) can be converted by the processor 42 of the controller 37 into power to be delivered by the motor 31. The setpoint is applied by the processor 42, which drives the block 26 actuators and the motor 31 via the output interface.

The processor 39 of the master control unit 36 is, in turn, programmed to:

control its 37 slave controllers,

take into account the or each singular point S communicated by each controller 37 at the end of the cycle performed by the or each associated forming station 10,

calculate a characteristic CS point from the point (s) S singular (s). This characteristic point CS may be the singular point S itself, communicated during a single cycle by a controller 37, or an average of singular points S communicated during several successive cycles by the same controller 37, or an average of singular S-points communicated during a single cycle by several controllers 37, or an average of individual S-points communicated over several successive cycles by several controllers

37; compare this characteristic point CS, derived (or calculated from) the measurements, with a theoretical point previously entered in the memory 38 of the master control unit 36 and corresponding to a model container,

if a discrepancy is decreed between the characteristic point CS and the theoretical point, issuing a corrected formation setpoint CF, comprising a modified pressure and / or fluid flow value to be delivered by the actuator block 26, or an instant for controlling the actuator block 26, or a profile for displacing the rod 28 (for example in the form of a speed curve of the rod 28 or of a power curve of the motor 31, as a function of the position rod 28) or another moving part;

load the corrected formation setpoint CF in the or each controller 37 controlled by the master control unit 36,

if necessary, communicate the characteristic CS point to the central control unit 33.

When no difference is decreed between the characteristic point CS and the theoretical point, no corrected forming instruction is issued by the processor 39, so that for the new forming cycle or several subsequent forming cycles, the controller 37 slave applies the forming instruction CF of the previous cycle (s).

In the hypothesis, mentioned above, of a correction of the formation setpoint CF, the new instruction CF is loaded in the slave controller 37 when the associated forming station 10 is in the buffer sector T, so that can be applied for the next forming cycle, from the loading of a new preform 2 to point 21 of load.

The angular position information of the wheel 23 is common to the controllers 37 and shared. It can be centralized at the level of the master control unit 36, whose processor 39 is in this case programmed to communicate, at predetermined intervals (in particular of a few milliseconds, for example 1 ms), via its communication interface 40, the instantaneous angular position of the wheel 23, as measured by the angular position sensor 24 in a polar coordinate reference centered on the axis of rotation of the wheel, denoted O. However, according to a preferred embodiment, the sensor 24 is connected directly, via a local computer network (LAN) to all the controllers 37. In this case, so that the information transmitted by the sensor 24 via the network is readable by the controllers, the sensor 24 preferably incorporates an analog / digital converter.

Each slave controller 37 is programmed to: take into account the instantaneous angular position of the wheel 23 as soon as this position is communicated to it by the master control unit 36 or directly by the angular position sensor 24,

deriving the angular position of the or each forming station associated with and controlled by the slave controller 37, and establishing the blowing curve from the pressures measured in the nozzle 25 of each associated mold, at times corresponding to each of these angular positions.

The calculation of the instantaneous angular position of each forming station 10 can be carried out in the following simple manner, taking as reference (i.e. the null angle) the point 21 of load (also noted C on the Figure 3).

An arbitrary fixed point is noted on the wheel 23, considered as a moving reference providing the angular position of the point C of load, denoted a and supplied by the position sensor 24, such that oc = COA.

B is the point corresponding to the relative angular position, denoted β, of the forming station 10, measured with respect to the point A and such that β = AÔB.

By noting Θ the absolute angular position of the forming station 10 in the fixed polar reference frame originating in the axis OC, this angular position Θ is such that Θ = CÔB = COÀ + AÔB = α + β.

D is the point of discharge (fixed in the polar reference frame OC axis), whose angular position, noted γ, is such that y = CÔD.

Thus, for any forming station, the processor 39 of the associated controller, in the memory 38 of which the values of the angles β and γ are written, is at each instant able to calculate the angle Θ by the formula indicated above and to determine if the forming station 10 is in the forming sector F, in which 0 < θ <2π-γ (the angles being expressed in radians), or in the sector T buffer, in which θ> 2π-γ.

It results from the architecture of the control system 34 that the tasks necessary for the operation of the forming unit 9 are shared between the master control unit 36 and the slave controllers 37 which are slaved thereto.

The tasks assigned to the controllers 37 include the actual control of the forming stations (in particular two stations 10 by each controller 37), the taking of measurement and the analysis of these measurements to deduce singular points S. These tasks are performed in real time, as the cycle progresses, and require rapid processing.

The tasks assigned to the control unit 36 include the analysis of the data communicated at each end of the cycle by the controllers 37, the decision as to whether or not to correct the CF instructions for forming, as well as the possible issuing and loading of corrected forming instructions CF. These tasks are performed for each deferred forming station while the latter is traveling through the buffer sector T when the setpoint corrections are intended to be applied from one cycle to the next, or for several cycles, when Control unit 36 performs point-point calculations based on averages of measurements made over several cycles.

This sharing of tasks makes it possible to limit both the volume of data to be processed and the speed with which these data must be processed by the control unit 36. In this way, the calculations necessary for the correct conduct of the forming operations are not limiting the rate of production.

As is also shown diagrammatically in FIG. 2, the heating unit 4 is also equipped with a dedicated control system which comprises a master control unit 46 and a series of slave controllers 47 that are slaved to the control unit. 46 master.

The master control unit 46 is computerized and comprises:

a memory 48 in which are registered control programs of the heating modules 5, a processor 49 connected to the memory 48 for applying the instructions of the programs, and

a communication interface 50 connected to the processor 49 for communication with external communicating entities.

Each slave controller 47 is a programmable logic controller, of the type described in W. Bolton, Programmable Logic

Controllers, Newnes, fifth edition, 2009.

More specifically, each controller 47 comprises:

a memory 51 in which are written programs for driving at least one heating module 5,

a processor 52 connected to the memory 51 to apply the instructions of the program,

a communication interface 53 connected to the processor 49 for communication with the master control unit 46 via its own communication interface 50,

an input interface 54 connected on the one hand to the processor 52 and on the other hand to the thermal sensor 20,

an output interface 55 connected on the one hand to the processor 52 and on the other hand to the power variator 19 and to the motors 14, 18 of the driving wheel 13 and the fan 17.

The controller 47 is programmed to perform the following operations:

control the or each heating module 5 to which it is associated, according to a charged DC charging (that is to say, recorded) in the memory 51;

from the temperature measurement (denoted T) issuing from the thermal sensor, establishing the instantaneous thermal profile of each preform 3, which may be in the form of an average temperature measured for the whole of the preform 3, a set of several temperature values at different heights on the body of the preform 3, or a curve giving the temperature T as a function of the height (denoted h) on the preform 3;

analyzing the thermal profile and extracting the coordinates from at least one singular point W (for example at a given height in the vicinity of the neck); communicating for each preform 3, or at predetermined intervals, the coordinates of the single point W to the master control unit 46.

The DC heating setpoint may comprise a power value delivered by the controller 19, a rotation speed of the motor 18 of the fan 17, or a speed of rotation of the driving wheel 13 (and therefore, consequently, a speed of preforms 3 - in other words the rate of production of the oven 4).

The processor 49 of the master control unit 46 is, in turn, programmed to:

control its 47 slave controllers,

take into account the or each singular point W communicated by each controller 47,

- calculate a characteristic CW point from the point (s) W singular (s). This characteristic CW point may be the singular point W communicated at a predetermined time by the controller 47, or an average of singular points W communicated during a predetermined period by the same controller 47;

comparing this characteristic CW point with a theoretical point previously entered in the memory 48 of the master control unit 46 and corresponding to a preform having given a model container,

if a difference is decreed between the characteristic CW point and the theoretical point, issue a corrected DC heating setpoint, comprising a modified value for the power of the drive 19, or for the speed of rotation of the motor 18 of the fan 17 or the driving wheel 13;

charging the corrected heating DC setpoint in the or each controller 47 controlled by the master control unit 46;

if necessary, communicate the characteristic CW point to the central control unit 33,

When no difference is decreed between the characteristic CW point and the theoretical point, no corrected heating setpoint is set by the processor, so that the controller 47 continues to control the (or each) heating module 5 according to the previous CC heating setpoint. As shown in the figures, the central control unit 33 of the installation 1 comprises:

a memory 56 in which are registered control programs of the control units 36, 46 of the dedicated control systems 34, these control units 36, 46 thus being slaved to the central control unit 33 (in others in other words, the control units 36, 46 are masters of the controllers 37, 47, and slaves of the central control unit 33);

a processor 57 connected to the memory 56 for applying the instructions of the programs, and

a communication interface 58 connected to the processor 57 for communication with the control units 36, 46.

The processor 57 of the central control unit 33 is programmed to control each control unit 36, 46, according to a processing instruction CF, CC loaded into the processor 39, 49 of each control unit 36, 46.

It has been seen that the control units 36, 46 can transmit to the central control unit the characteristic CS, CW points.

This transmission allows the processor 57 of the central control unit 33 to control the operation of each processing unit 4 (respectively 9) according to measurements from another processing unit 9 (respectively 4).

More specifically, the processor 57 of the central control unit 33 is programmed to:

to take into account at least one characteristic CS, CW point communicated to it by a first control unit 36 (respectively 46),

compare this characteristic point with a theoretical point written in the memory 56 of the central control unit 33,

if a discrepancy is decreed between the singular point and the theoretical point, issuing a corrected processing instruction CC, CF addressed to a second control unit 46 (respectively 36), and loading this setpoint CC, corrected treatment CF in the second unit 46 (respectively 36) of control.

This sequence of operations may in particular be triggered in the case where a first setpoint correction performed at a control system 34 (respectively 35) dedicated to a unit 9 (respectively 4) given processing does not delete (or does not decrease), the following cycle (or a predetermined number of cycles), the difference found between the point CS, CW characteristic and the theoretical point.

It can also be triggered in the case where it is known (and therefore programmed) that only the correction of a DC instruction, CF processing to the second unit 46 (respectively 36) control is likely to affect (and therefore to correct) the measurements made on the first unit 9 (respectively 4) treatment.

In the example illustrated, the quality of the final container 2 obtained at the output of the forming unit 9 depends in particular on the heating temperature T, which is set in the heating unit 4. The heating temperature T of the preforms 3 may in fact vary according to:

the intensity of the radiation delivered by the heating modules, which depends on the electrical power delivered to them, modulated by the variator 19,

the power of ventilation, regulated by the speed of rotation of the fan 17, which is modulated by the motor 18,

- The speed of travel of the preforms 3, which is modulated by the motor 14 of the wheel 13.

Thus, it is understood that a change in DC set point affecting the heating temperature T within the heating unit 4 will result in a modification of the blowing curve, and in particular the position of the singular point S detected in this blowing curve. ci by the processor 39 of the controller 37. This set point change CC is performed according to the following procedure, thanks to the programming described above:

after establishing the blowing curve, the controller 37 analyzes it and extracts the coordinates of the singular point S

(typically point B), and communicates these coordinates to the control unit 36 of the forming unit 9;

having decreed that a change in the forming set point CF is insufficient to obtain the desired correction of the position of the singular point S on the blow-off curve at the next cycle or in a predetermined number of subsequent cycles, the unit 36 of control communicates the coordinates of the characteristic CS point to the central control unit 33;

the control unit 33, programmed for this purpose, determines that the blowing curve can be corrected by a change in the heating temperature T, or the speed of rotation of the fan 17, or the speed of scrolling preforms 3 (in other words the rotational speed of the wheel 13) and provides a corrected heating DC setpoint to the attention of the control unit 46 of the heating unit 4;

the central control unit 33 loads the heating DC setpoint thus corrected in the control unit 46 of the heating unit 4; the control unit 46 controls the controllers 47 by applying the heating setpoint CF thus corrected.

This architecture has several advantages.

Firstly, it makes it possible to decongest the control system 32 of the installation by sharing the tasks between several levels of control connected to each other according to the master-slave principle:

the controllers 37, 47 are programmed to conduct low level and short time operations, including (analog) control of mechanical components;

the control units 36, 46 are programmed to conduct intermediate level operations and relatively longer times, including the calculation of characteristic points (in particular averages) as a function of measurements received from the controllers 37,

47, the comparison with reference values, the issuing of instructions (possibly corrected) and the driving, according to these instructions, of the controllers 37, 47;

the central control unit 33 is programmed to conduct higher level operations over long periods, including the taking into account of data communicated by the control units 36, 46, the issuing of setpoints and the steering, depending of these instructions, control units 36, 46.

Secondly, this architecture allows a dialogue between the different units 4, 9 of treatment of the installation 1, without it being necessary to centralize all the operations within the central control unit, to which only be affected decision-making tasks, correction of setpoints CF, CC and loading instructions CF, CC corrected in control units 36, 46 which are enslaved.

Thirdly, thanks to the dialogue between the different control levels, the programming of the entire control system 32 can be centralized at the higher level, that is to say in the central control unit, which can relay to the control units. Units 36, 46 control the program dedicated to them as well as the program dedicated to the controllers 37, 47, the control units 36, 46 in turn relaying to the controllers 37, 47 the program dedicated thereto. It is therefore not necessary to load the programs individually in each controller 37, 47, or even in each control unit 36, 46. This results in a simplification of the programming of the installation, and increased productivity.

Fourthly, this architecture makes it possible to carry out a transverse feedback, that is to say to control a modification of the setpoint applied by a processing unit - typically the heating unit 4 - as a function of measurements carried out within a other processing unit - typically the forming unit 9. The quality of the containers produced is thereby improved.

Claims

1. System (32) for controlling an installation (1) for manufacturing containers (2) from thermoplastic blanks (3), said installation (1) comprising at least two units (4, 9) of treatment of the blanks (3) or containers (2), each equipped with at least one station (5, 10) for treating the blanks (3) or containers (2), characterized in that it comprises a unit ( 33) control center of the installation (1), at least two control units (36, 46) controlled by the central control unit (33) and associated respectively with a processing unit (9, 4), and at least two controllers (37, 47) each slaved to a control unit (36, 46) each associated with at least one processing station (10, 5).

2. System (32) according to claim 1, characterized in that the central control unit (33) is programmed to:

control each slave control unit (36) according to a set point

(CF) treatment loaded in the control unit (36),

take into account at least one characteristic point (CS) at the central unit (33) by the control unit (36),

comparing this characteristic point (CS) with a theoretical point, if a difference is decreed between the characteristic point (CS) and the theoretical point, issuing a corrected processing instruction (CC) destined for a second control unit (46) ,

- load the corrected processing instruction (CC) into the second control unit (46).

Control system (32) according to claim 2, characterized in that each control unit (36) is programmed to:

- Control each slave controller (37) according to the processing instruction (CF) loaded by the central unit (33),

taking into account at least one singular point (S) resulting from a measurement made on at least one processing station (10) of a first controller-processing unit (9) (37), calculate a characteristic point (CS) according to the singular point (s),

comparing the characteristic point (CS) with a theoretical point, if a difference is decreed between the characteristic point (CS) and the theoretical point justifying a modification of the processing instruction (CC) of another processing unit (4), communicate the characteristic point (CS) to the central control unit (33).

Control system (32) according to claim 3, characterized in that each controller (37) is programmed to:

control at least one treatment station (10) according to the processing instruction (CF),

ordering at least one measurement at the processing station (10),

analyze the curve and extract the coordinates of a singular point (S),

communicate the singular point (S) to the control unit (36).

5. Installation (1) for manufacturing containers (2) from thermoplastic blanks (3), this installation comprising at least two units (4, 9) for treating the blanks (3) or containers (2) , each equipped with at least one station (5, 10) for treating the blanks (3) or containers (2), characterized in that it further comprises a control system (32) according to one of the claims preceding.

6. Installation (1) according to claim 5, characterized in that one of the processing units is a unit (4) for heating the blanks (3), and another processing unit is a forming unit (9) equipped with at least one station (10) for forming the containers (2) from the blanks (3).